1. Field of the Invention
The present invention relates to an apparatus for drying cut tobacco and more particularly to an apparatus for drying tobacco under relatively high humidity drying conditions.
2. Discussion of the Prior Art
In the manufacture of cigarettes and like articles, it is the usual practice to reduce tobacco, the term being used herein to include both lamina and stems, to a particle size appropriate for manufacturing cigarettes. The moisture content of the tobacco is generally increased prior to this size reduction processing in order to minimize tobacco breakup and provide a material of uniform particle size. Furthermore, in order to process the treated tobacco in the manufacturing of cigarette rods, it is necessary to reduce the moisture content of the tobacco to a level below that which the tobacco is at after treatment by casings, flavorings and other additives. The actual drying process has a direct impact upon the quality of tobacco utilized during cigarette manufacturing because of the effect the drying process has upon the tobacco material itself.
Additionally, drying of tobacco after the addition of flavorings and casings has a direct impact upon the quality of the tobacco itself. If, during drying, the tobacco is subjected to rigorous agitation or contact with stationary surfaces, the tobacco material can be damaged by breakup thus decreasing the filling capacity of the tobacco. This unwanted result is also achieved when drying under low humidity conditions. It is therefore necessary to dry the moist tobacco under high humidity conditions while also preventing damaging contact to the tobacco material.
U.S. Pat. No. 4,167,191 teaches a process for high humidity drying of tobacco material in order to reduce the moisture content of expanded tobacco while minimizing yield losses and reducing particle lamination while maintaining filling power. The air temperature used to dry the tobacco is within a range of around 250.degree. F. to about 650.degree. F. in the presence of an absolute humidity at a level above that which will provide a wet-bulb temperature reading of at least about 150.degree. F.
U.S. Pat. No. 4,315,515 teaches a tobacco drying apparatus having a plurality of expansion chambers which effect a drying of the tobacco within a high humidity environment. The drying chambers are utilized to reduce the velocity of the air flow through the apparatus as well as a dryer means to effect drying of the air entrained tobacco to the desired moisture level. However, the apparatus requires long extensions of air ducting as well as several air redirection areas or elbows which cause the tobacco to come into contact with the walls of the ducts in the air chambers causing tobacco breakup, sanitary, cleaning and other problems within the apparatus.